1. Field of the Invention
The present invention relates to an exposure apparatus and a method for manufacturing a device including a fine pattern such as a semiconductor device or a liquid crystal display device. More particularly, the present invention relates to an exposure apparatus and a method using an immersion method for manufacturing a device including a fine pattern such as a semiconductor device or a liquid crystal display device.
2. Description of the Related Art
A reduced projection exposure apparatus which transfers a pattern formed on a mask onto a substrate coated with a photosensitive material by reduced projection is used in manufacturing a semiconductor device such as a large scale integrated circuit (LSI) or a very-large-scale integrated circuit (VLSI) which includes an extremely fine pattern. With advancement of highly-integrated semiconductor device, a demand for a finer pattern is increasing. In order to meet such a demand, resist process as well as an exposure apparatus which is capable of producing a finer pattern have been developed.
Generally, two methods are used in improving resolution of an exposure apparatus. One is shortening of exposure wavelength and the other is increasing of numerical aperture (NA) of a projection optical system. As for the exposure wavelength, a krypton fluoride (KrF) excimer laser beam with an oscillation wavelength of about 248 nm or an argon fluoride (ArF) excimer laser beam with an oscillation wavelength of about 193 nm is used in place of i-line light source with a wavelength of 365 nm. Further, a fluorine (F2) excimer laser with an oscillation wavelength of about 157 nm is being developed.
On the other hand, as a different method for improving resolution, a projection exposure method using immersion method is receiving attention. Conventionally, a space between a final face (i.e. a light exiting surface of a lens (final lens) nearest the image side) of a projection optical system and a face of a substrate (for example, wafer) to be exposed with light is filled with gas. On the other hand, in a case of the immersion exposure method, this space is filled with liquid.
The immersion method can improve resolution even when a light source of the same wavelength as the conventional light source is used. For example, if a space between the projection optical system and the wafer is filled with pure water (having a refractive index of 1.44) and if a maximum incident angles of a light beam which forms an image on the wafer are the same in the immersion method and the conventional method, then resolution of the immersion method increases 1.44 times compared to the conventional method. This is equivalent to increasing the NA of the projection optical system of the conventional method by 1.44 times. Thus, the immersion method can achieve a resolution of NA of 1 or more which may not be possible to achieve by the conventional method.
The immersion method which fills a space between a final face of a projection optical system and a wafer face with liquid is discussed, for example, in Japanese Patent Application Laid-Open No. 2005-19864. The method discussed in Japanese Patent Application Laid-Open No. 2005-19864 is intended to reliably fill a gap between a final face of a projection optical system and a substrate with liquid in an exposure apparatus using the immersion method.
As illustrated in FIGS. 16A through 16C, the exposure apparatus includes a liquid supply nozzle 38 which is arranged in a first direction as seen from a periphery of a projection optical system 13. When a substrate stage on which a substrate W is mounted is moved in a second direction which is a direction opposite the first direction liquid 40 is supplied onto a surface of the substrate W through the liquid supply nozzle 38 in the direction of an arrow and a liquid film is formed on the surface. The liquid 40 is continuously supplied onto the surface of the substrate W through the liquid supply nozzle 38 so that the liquid film is continuously spread on the substrate W while the substrate W is moved. The liquid 40 is collected by a liquid collection nozzle 39. A plate (hereinafter referred to as a coplanar plate) is arranged to maintain the immersion area on the substrate stage at a height substantially the same as the substrate W.
Japanese Patent Application Laid-Open No. 2005-116570 discusses an exposure apparatus having a photodetector on a wafer stage and using an immersion method. The method discussed in Japanese Patent Application Laid-Open No. 2005-116570 aims at optimizing an exposure state based on a light-receiving result of the photodetector in order to realize the exposure apparatus which is capable of exposing with high precision. The exposure apparatus exposes a substrate with light by irradiating the substrate through a projection optical system and liquid. The substrate is arranged on an image plane side of the projection optical system. The exposure apparatus includes a photodetector configured to receive light which passes a slit plate of the projection optical system, and a temperature sensor configured to detect temperature of the liquid. The slit plate is arranged on the image plane side of the projection optical system. The liquid fills a space between the projection optical system and the slit plate. A detection result obtained by the photodetector and a measurement result obtained by the temperature sensor are used in calculating performance including image forming performance. Then, the performance information is reflected at the time of the exposure.
Japanese Patent Application Laid-Open No. 2005-191557 discusses a method for preventing liquid from remaining on a substrate table. The method is used in an immersion exposure apparatus which includes a substrate table configured to hold a substrate. A plate member having a liquid-repellent flat surface is arranged replaceably on the substrate table. Further, a reference member having a liquid-repellent surface is replaceably arranged on the substrate plate. Polytetrafluoroethylene is used to give a liquid-repellency to the surfaces.
International Publication No. 2005/022616 discusses a method for removing liquid remaining in an immersion exposure apparatus. International Publication No. 2005/022616 discusses problems of liquid dripping from a liquid supply-and-collection nozzle of a projection optical system, watermarks or stains of residual water, scattering of residual water on a reference mark, and degraded precision of an interferometer due to liquid attached to an interferometer reflection mirror when collection of the liquid is insufficient. In order to solve these problems, International Publication No. 2005/022616 discusses a liquid removing mechanism for blowing gas which is capable of changing a blow speed of gas, a vibrating apparatus which removes residual water by vibration, and gutters or eaves which are arranged on a wafer stage to prevent liquid from attaching thereto. Further, blowing gas and collecting residual water from a drain unit is also discussed as a method for removing residual water on the reference mark.
Japanese Patent Application Laid-Open No. 2005-38874 discusses a device having a plurality of wafer stages which is used in an immersion exposure apparatus. According to the device, a stage can be moved in a non-contact state between movable bodies with enhanced throughput. It is described that the device can be adapted to an immersion exposure apparatus. Two stages which are movable in a two-dimensional plane are supported and driven in the non-contact state with respect to first and second movable bodies. The stages can be micro-driven in two axial directions which are perpendicular to each other in the two-dimensional plane with respect to each movable body. The stage is moved from one movable body to the other while the movable bodies are in proximity to each other. When the stage moves from one movable body to the other, since the stages can be micro-driven while the movable bodies are in proximity to each other, the stages can be moved between the movable bodies in a non-contact state and with enhanced throughput.
Arranging a reference member or a reference mark on a wafer stage is discussed in Japanese Patent Application Laid-Open No. 2005-116570, Japanese Patent Application Laid-Open No. 2005-191557, and International Publication No. 2005/022616. A liquid-repellent coplanar plate arranged in a periphery of a substrate and arranged at a substantially same height as the substrate is discussed in Japanese Patent Application Laid-Open No. 2005-191557. A method used for removing residual water on a reference mark is discussed in WO2005/022616. Further, a method used for removing residual water on a surface of an interferometer mirror is discussed in International Publication No. 2005/022616. An immersion exposure apparatus including two wafer stages is discussed in Japanese Patent Application Laid-Open No.2005-38874. However, When the liquid is removed, a drying process by blowing gas needs to be performed or time is taken for transferring liquid which reduces throughput. The present invention aims at solving the above-described problems in the conventional techniques.